Evaporative emission control systems are widely used in internal combustion engine powered motor vehicles to prevent evaporative fuel, i.e., fuel vapor, from being emitted from the fuel tank into the atmosphere. Typically, a vapor management valve (or evaporation canister purge valve) can be found in an internal combustion engine powered motor vehicle to control evaporative emission.
The vapor management valve is a normally closed solenoid that is mounted in line between an evaporation canister and the intake manifold of an internal combustion engine. In operation, when the Electronic Engine Control (EEC) assembly energizes the solenoid, the solenoid opens, thus allowing the intake manifold vacuum to draw fuel vapors from the canister into the cylinders for combustion. In contrast, when the EEC assembly de-energizes the solenoid, fuel vapors from the fuel tank are stored in the evaporation canister.
Federal law has been implemented to regulate the emission of fuel vapors into the atmosphere. As a result, it has become necessary to employ an on-board diagnostic system capable of detecting deficiencies in evaporative vapor emission control components and identifying such deficiencies so that corrective measures may be taken. In the event that one or more evaporative emission control components malfunctions, fuel vapors may be vented improperly resulting in reduced engine performance and possible release of vapors into the atmosphere.
The known prior art attempts to detect deficiencies in evaporative vapor emission control components by providing additional hardware to the vehicle system thereby adding additional cost to the vehicle which is passed on to a consumer.
In addition to adding cost to the vehicle, the additional hardware increases the number of parts that can fail, thereby increasing warranty concerns to the manufacturer of the vehicle.